Can salt power the future?

The clean energy transition runs on batteries – and those batteries are often made in not-so-clean ways.

Most of today’s batteries are lithium-ion batteries. They’re used in electric vehicles, data centers and stationary power grids for solar panels and wind turbines, as well as in everyday items like phones, laptops and electric scooters.

Lithium requires massive amounts of water to extract and refine – about 2 million liters of water per metric ton of lithium, according to the Institute for Energy Research.

For instance, in Chile, the world’s second-largest producer of lithium, the industry uses a brine mining process, which diverts already scarce freshwater from local Indigenous communities and is causing severe harm to nearby fragile wetland ecosystems.

What’s more, lithium-ion batteries require heavy metals like cobalt, nickel, manganese and copper in their cathodes, which draw the ions from the anode when the battery is discharging.

Most of the world’s cobalt reserves are located in the Democratic Republic of the Congo, where lithium mines routinely exploit workers, contaminate water sources, and release toxic dust and particulates into the air.

Aside from ethical considerations, geopolitics poses its own challenges. China dominates the market, with 68 percent of global cobalt refining capacity, 72 percent of lithium refining capacity and 83 percent of lithium-ion manufacturing capacity.

These pitfalls have scientists and companies alike looking for alternative sources of battery power.

A few examples include aqueous zinc, flow batteries and even gravity – that works by converting kinetic energy into electricity.

But there’s a cheap, abundant and readily available material that is leading the race to replace lithium as the main ingredient in batteries.

Salt.

Enter sodium

Jean-Marie Tarascon, a professor of physics and solid state chemistry at the Collège de France, has believed in the superiority of sodium for at least 15 years.

As founder and director of the research network RS2E, he led a team that developed a sodium-ion battery at the Collège and at the University of Picardie Jules Verne – rather fittingly, considering Verne first envisioned a fictional salt battery in his book, Twenty Thousand Leagues Under the Sea.

“The main driver in my case was sustainability,” says Tarascon. “Back in 2010, it was obvious that the world would adopt lithium-ion batteries and we would run out of this resource.”

“The decision was to find an alternative – which is why we moved to sodium.”

Sodium-ion batteries have a similar chemical behavior to lithium-ion batteries, albeit without the negative environmental impacts, says Shan Zhang, a researcher at Chalmers University of Technology in Gothenburg, Sweden.

“The manufacturing process is also similar, which means that you don’t really need to test the production line that much,” she adds. “You can use existing production lines and make some adjustments for the salt battery.”

Zhang says sodium batteries are also safer than their lithium counterparts and perform better in extreme temperatures.

Lithium-ion batteries have been responsible for countless fires, notably including one at a California battery storage plant earlier this year that burned for days and prompted the evacuation of around 1,200 local residents.

In 2024, Zhang led a study that examined the future climate impacts of different types of salt batteries, focusing on carbon emissions.

Her team found that by 2050, the use of renewable energy to manufacture batteries could potentially reduce its climate impact by 43 to 57 percent compared to 2020 levels.

“The climate impact drops the further into the future we go, from the manufacturing processes, the mining, as well as the upstream processes,” she says. “It happens along the whole production chain.”

But the chemicals used in the cathode are still a concern, she says, and will need to be tackled with more investment in sodium-ion battery research.

Finding a niche

So, what’s stopping a bigger uptake of sodium-ion batteries? It’s mostly the low price of lithium, keeping it competitive with sodium.

After skyrocketing to a record USD 83,000 per tonne in November 2022, the price of lithium has been falling ever since, hitting a low of just USD 8,400 per tonne last month, as electric vehicles (EVs) have been selling more slowly than expected.

Another obstacle is that sodium is less dense than lithium, which means more space and energy is needed to hold the same charge.

This results in a bigger, heavier battery, which is less than ideal in your car or in your phone, for example.

Rather than fully replacing lithium, sodium “needs to find its niche applications” where volume and weight are not an issue, says Zhang.

As scientists continue to work on improving their energy density, one suitable place for sodium-ion batteries is in stationary energy storage systems, where energy can be stored and discharged when needed to balance out the electrical grid.

In fact, Bloomberg New Energy Finance (BNEF) is currently projecting a 15-percent market share for sodium-ion batteries in energy storage by 2035, up from 1 percent today.

In the United States, Silicon Valley-based Natron Energy is manufacturing sodium-ion batteries for installation in data centers and cloud computing companies, as well as EV fast chargers.

It recently broke ground on a USD 1.4 billion new plant in North Carolina, representing a 40-fold increase in capacity.

Meanwhile, in the U.K., Faradion, a subsidiary of India’s Reliance New Energy Ltd., is making sodium-ion batteries for transportation, storage and back-up power.

And in France, TIAMAT, a company that Tarascon serves as a scientific advisor, invented the first sodium-ion battery designed for use in a commercial product: a cordless power drill.

Last month, it signed a contract with U.S. tech firm Endeavour to make batteries for AI data centers.

Driving on salt

The biggest adopter of the sodium-ion battery, however, is China. The country already dominates the market in lithium-ion batteries, which is one reason it has easily made the switch, says Zhang.

Chinese firms have already invested over USD 7.6 billion in sodium-ion technology, with 27 new production facilities announced in 2024 alone.

Companies like Yadea, HiNa, and Contemporary Amperex Technology (CATL) are now building a competitive edge in the global sodium-ion battery market, taking another big step in the country’s clean-technology industry.

And unlike their Western counterparts, they’re already putting sodium-powered vehicles on the road.

Yadea, for example, is starting to sell electric mopeds powered by sodium after a successful pilot project with 150,000 food delivery couriers in Shenzhen.

While these two-wheelers only have a range of about 70 kilometers, the manufacturer has built battery-swapping stations where owners can switch out depleted batteries in less than a minute, rather than having to wait hours to recharge them.

CATL, the world’s largest battery manufacturer for EVs and energy storage, announced a plan earlier this year to mass-produce sodium-ion batteries for heavy-duty truck and cars under a new brand called Naxtra.

Electric motorcycles and mopeds are already ubiquitous in China, with some 55 million sold in 2023 alone.

Now, the country’s forays into sodium battery-powered vehicles could create huge potential for expansion across the Global South, particularly in Asia and Africa, says Kate Logan, director of the China Climate Hub and climate diplomacy at the U.S.-based Asia Society Policy Institute.

“Because the use of two- and three-wheelers is concentrated in the Global South, these markets will be even more important to Chinese companies’ overall strategies from the get-go, rather than driven by factors like trade tensions and lack of access to Global North markets,” she explains.

Converting these bikes and trikes wholesale to electric power across Global South markets will have a significant impact on both emissions and fossil fuel use, she adds.

For his part, Tarascon sees a big change coming in the size of cars over the next decade in the Global North, too.

“We are going to have smaller cars in the cities, more taxis, and more short-range vehicles, so automatically, the sodium-ion battery will have a big game to play,” he says.

“If I look at the future, this technology will certainly be improved, and I think it will gain a big part of the market because there is a huge demand for battery energy, and lithium-ion cannot make it all.”